We are completing our synthesis of l Beta-deuterated C19 and C18 estrogen precursors. We expect to evaluate these materials kinetically for isotope effects when they are aromatized enzymatically. We are continuing our work on evaluating the enzyme properties of the aromatase from rat ovary. This will include the effects of antibodies to cytochrome b5 on estrogen biosynthesis, and the evaluation of additional compounds for spectral interactions. Also, we hope during this period to attempt to solubilize the aromatase from this system.